Screen stencil-printing machines



March 27, 1956 J. N. M LAURIN 2,739,530

SCREEN STENCIL-PRINTING MACHINES Filed Jan. 22, 1955 2 Sheets-Sheet 1U'Amss N- Me. Lnu m M 26 A 7'7'OR/VEY March 27, 1956 J. N. M LAURIN2,739,530

SCREEN STENCIL-PRINTING MACHINES Filed Jan. 22, 1955 2 Sheets-Sheet 2FIG 7. V'Amzs 1v. McLAuRIN BY. 5W

ATTORNEY United SCREEN STENCIL-PRENTING MAQHINES James N. McLaurin,Edinburgh, Scotland, assignor of one-half to E. T. Marler Limited,London, England Application January 22, 1953, Serial No. 332,591

2 Claims. (Cl. 101-123) This invention relates to silk or like screenstencilprinting machines of the kind in which a resilient squeegee orwiper is reciprocated across the screen and is given a rocking movementat the end of the printing stroke to lift the wiper from the screen.

The machine of the present invention comprises a screen frame pivotallymounted near its rear end on the fixed bed frame of a horizontalprinting bed and counterbalanced or otherwise controlled so that thescreen frame normally tilts upwards about its pivot into an openposition, a resilient squeegee or wiper mounted on a carriagereciprocable across the screen by reciprocating mechanism, means formounting the squeegee or wiper for rocking movement about a horizontalaxis on the carriage, an electric motor arranged to drive the carriagereciprocating mechanism, a switch controlled by tilting opening movementof the screen frame to stop the motor when the screen frame is tilted,releasable locking mechanism for locking the screen frame to the bedframe during printing and released by means operated at the end of theprinting stroke of the carriage to release the screen frame and to allowthe latter to tilt upwards for the withdrawal of the printed sheet fromthe printing bed, and mechanism for rocking the wiper to engage thewiper with the screen during the printing stroke and for lifting thewiper clear of the screen at or near the end of the printing stroke andduring the return stroke of the reciprocating carriage towards the frontend of the machine, in readiness for wiping over the screen during theworking stroke of the wiper and simultaneous printing operation.

The momentum of the moving carriage and its driving mechanism is suchthat, after the motor has been stopped by the tilting of the screen, thecarriage continues its travel and completes part of its return stroke,the remainder of the return stroke being completed when the screen frameis closed down upon the bed frame by manual operation after the nextsheet to be printed has been laid on the printing bed. This partialreturn movement of the reciprocating mechanism reduces the interval oftime required for the actual printing operation.

A machine according to the invention is illustrated in the accompanyingexplanatory drawings, whereon:

Fig. l is a diagrammatic side View of the machine.

Pig. 2 is a fragmentary perspective view showing the carriage with thewiper commencing the printing stroke.

Fig. 3 is a view looking at the rear of the color scoop at thecommencement of the forward or return stroke.

Fig. 4 is a fragmentary perspective view showing the scoop bein liftedby a lifting rail.

Figs. 5, 6 and 7 are end views of the carriage showing various positionsof the wiper and scoop.

An electric motor 1 is mounted on an extension 2a of a screen frame 2rearward of a pivot 3 for the screen frame, and a counterbalance weight4 is provided for ensuring upward tilting of the screen frame, which isnormally locked to a bed frame 5 by spring catches 6.

"' 7 of the bed frame 5 and the counterweight 4 is suspended The screenframe pivot 3 is supported in upright members from a cable 8 passingover a pulley 9 on the upright members 7 to an anchorage at the front ofthe screen frame 2 which is provided at the front with a handle 10 forclosing or lowering the screen frame. A screen (not shown) is stretchedacross the screen frame in known manner and reciprocating over thescreen is a carriage denoted by the general reference A in Fig. l. Thecarriage comprises a rotatable cross shaft 11 carried at its ends inslide blocks 12 mounted on rollers or guides running on rails 13 housedin side casings 14 on the screen frame. At or near the end of theprinting stroke the said slide blocks 12 are adapted to engage resilientabutments 15 operatively connected by rods or cables 16 to the .lockingcatches 6 of the screen frame to release the catches. Reciprocation ofthe carriage is effected by securing on each end of the cross shaft 11 adriving arm 17 pivotally connected at its outer end to an endless chain18 housed in the side casing on the screen frame, said chain passingaround end sprockets 19 and 20 driven from the motor shaft. Thearrangement is such that the cross shaft 11 is rocked by the driving arm17 as the pivotal connection between the driving arm and the chainpasses around the end sprockets. A wiper 21 is carried by arms 22 freelymounted for limited angular movement on the cross shaft between a stop(not shown) and adjustable stops 23a on arms 23 fixed on the cross shaftso that the resilient pressure of the wiper on the screen can beadjustably controlled by adjusting the stops 23a to vary the pressure ofthe arms 23 on the Wiper 21. Fixed arms 24 on the cross shaft andpreferably unitary with the arms 23, carry a scoop 25 in a position suchthat the scoop is lowered and the wiper is raised as shown in Fig. 5 andvice-versa when the cross shaft is rocked. The scoop is pivotallymounted at 26 on carrying arms 27 and is controlled by a spring orsprings 28 for limited rocking movement on the carrying arms 27 in orderto hold the scoop in resilient contact with the screen during the timethe scoop is in contact therewith, as shown in Fig. 5, and pins orprojections 29 on the ends of the scoop are arranged to run on tracks orlifting rails 30 in the side casings on the screen frame. The tracks orrails 36 are of such a length that the scoop is raised as in Fig. 6 overthe greater part of its travel and is released as shown in Fig. 7 torest on the screen near the end of the forward stroke of the carriage.As the carriage approaches the rear or pivoted end of the screen frame,the cross shaft 11 is rocked by the chains 18 to lift the wiper as inPig. 5. As the scoop moves forwards it descends in rear of the colorleft by the wiper and collects the color as shown in Fig. 5. The scooprises during the initial forward stroke of the carriage, holding thecolor as shown in Fig. 6 during the stoppage of the machine, andcarrying it forwards again when the screen frame is closed down on tothe bed frame and the motor is thereby automatically re-started. At theforward end of the forward stroke, the pins or projections 29 on thescoop drop off the rails 30 and the scoop deposits the color on thescreen as shown in Fig. '7 in a position in which it is immediatelythereafter engaged by the movement of the wiper into operative positionby rocking of the cross shaft as its connections to the chains passaround the front sprockets 19.

Color is fed to the screen by a reservoir 31 mounted across the screenframe and having a discharge outlet or slot controlled by a slide valvewhich is normally closed by spring means and is temporarily openedduring the return of the carriage, a projection on the carriage trippinga trip device operatively connected to the slide valve to open itmomentarily, this color charge being picked up by the scoop on the nextreturn stroke of the carriage.

The operation of the machine is as follows:

Starting with the wiper in the position of rest, the motor having beenstopped by lifting the screen frame, the carriage of the wiper and scoopwill have moved forwards, thus covering part of the forward ornon-printing stroke before coming to rest. The operator places a freshsheet in register position on the base board or bed 32 and closes thescreen frame down upon the bed frame. In doing so, an electric switch 33 is released and the motor comes into operation, driving the chains 18in a direction to move the carriage towards the front of the machine,the carriage being drawn by the arms 17 engaging the upper run of thechains. As the connection of the arms to the chains passes over thefront sprockets, the wiper or squeegee comes into action, as shown inFig. 2 and the printing operation takes place during the movement of thecarriage and wiper rearwards. When the carriage strikes the abutments15, the catches 6 are released and the screen frame tilts upwards aboutthe pivot 3 under the action of the counterbalance weight. The wiper isthus lifted clear of the screen and of the color thereon. The action oftilting the screen frame actuates the switch to stop the motor, but themomentum of the moving parts is sufiicient to carry the arms 17 over theend sprockets 2i) and to drive them forward, thus bringing the scoopinto operation, lifting the color left by the Wiper and carrying thecolor part of the way up the screen frame in readiness for depositing itin readiness for the next printing stroke. When the screen frame isagain closed down, the scoop rides on the rail 30 as in Fig. 6, andfinally deposits the color on the screen as shown in Fig. 7 shortlybefore the wiper comes into operation as in Fig. 2 to distribute thecolor over the screen.

During the initial forward run of the carriage by momentum, a projectionon the carriage trips a valve beneath the color reservoir 31 to feed aregulated amount of color on to the rear part of the screen in readinessto be picked up by the scoop on its next forward run.

I claim:

1. A screen stencil-printing machine comprising a fixed bed frame, ahorizontal printing bed in said frame, a screen frame pivotally mountednear its rear end on said bed frame, means urging said screen frame intoa normally upwardly tilted position, releasable locking means forlocking the screen frame to the bed frame, a screen mounted in saidscreen frame, a carriage reciprocable across the screen in said screenframe, reciprocating mechanism for reciprocating said carriage, a rockshaft mounted on said carriage for rocking movement about a horizontalaxis, arms having limited angular movement about said shaft, a resilientwiper carried by said arms, fixed arms on said shaft adapted to engagesaid wiper during the printing stroke to exert resilient pressure on thewiper during printing, secondary fixed arms on said shaft carrying acolor scoop in such a position that the scoop is lowered into contactwith the screen when the wiper is raised clear of the screen andvice-versa, an electric motor operative to drive said reciprocatingmechanism, a switch controlled by tilting movementof said screen frameto stop the motor when the screen frame is in an upwardly tiltedposition and to start the motor when the screen frame is closed downupon the printing bed, operation of the motor causing reciprocation ofthe carriage, rock shaft and wiper, means actuated by the carriage nearthe end of its printing stroke to release said locking means and permitsaid screen frame to tilt upwards, and mechanism for rocking the wipershaft to engage the wiper with the screen during the printing stroke andto lift the wiper clear of the screen at or near the end of the printingstroke.

2. A printing machine as specified in claim 1, having the scooppivotally mounted on said secondary arms and resiliently controlled forlimited rocking movement thereon to hold the scoop in resilient contactwith the screen during the time the scoop is in contact therewith, andmeans on the screen frame adapted to coact with a projection on thescoop to raise the scoop clear of the screen and to hold color on thescoop during the greater part of its forward travel and to permit thescoop to rest on the screen near the end of the forward stroke of thecarriage and before commencement of the printing stroke.

References Cited in the file of this patent UNITED STATES PATENTS1,815,021 Bland a- July 14, 1931 1,922,710 Owens Aug. 15, 1933 1,966,416Parmele et al. July 10, 1934 2,207,818 Perry et al. July 16, 19402,267,596 Montague et al. Dec. 23, 1941 2,421,210 Louft May 27, 19472,571,685 DAutremont Oct. 16, 1951 2,637,269 Thomas May 5, 19532,651,988 Thomas et al Sept. 15, 1953

